1. Field of the Invention
This invention pertains to devices for monitoring the longitudinal position of moving conveyor belts, and more particularly, to means for stabilizing the position of light sensing types of position monitoring means relative to a moving conveyor belt.
2. Description of the Prior Art
Where customer specialty orders are filled, requiring selection of a moderate number of products from among a large number of different available products, it is often useful to fill the orders by computer-controlled conveyor lines, with the different products being stored in dispensing magazines on either side of a conveyor line. For example, a series of orders may be placed on the conveyor with the orders being defined by preselected space allotments on the conveyor and with the selected products for each order being placed in the proper alloted conveyor space as the conveyor moves past the appropriate dispensing stations. In such an arrangement, it becomes important to carefully monitor the longitudinal movement of the conveyor so as to determine as precisely as possible at any given time its longitudinal position.
One means of indexing the longitudinal movement of a belt conveyor uses a light source and photodetector with the line-of-sight between the source and detector being oriented perpendicularly to the plane of the conveyor belt. Thus, the light rays associated with the photodetector are directed to pass through a linear series of small apertures in the conveyor belt, or they are arranged to be reflected from a linear series of light reflecting areas on the conveyor belt. One troublesome problem which arises with such an arrangement is the problem of precisely positioning the edge of the conveyor belt relative to the photodetector in order to assure accurate readings.